The present invention relates to a semiconductor device and, more particularly, to a metal pad open process for manufacturing a semiconductor device.
In general, a pad is a part which is connected with a wire in a wire bonding process of the assembly process which forms a semiconductor chip, while a semiconductor device communicates signals between the inside and the outside through the pad.
In addition, in the manufacturing process of the semiconductor device, when a plurality of chips are prepared on wafers, a passivation layer is formed as a final protection layer in order to protect the chips from an undesirable environment. After the formation of the passivation layer, the pad is opened by removing the passivation layer on the pad in order to connect a lead line which is to be connected with an outside circuit in the package process with the pad of chip.
FIGS. 1a to 1g are cross-sectional views showing the manufacturing method of a semiconductor device according to the related art.
Referring to FIG. 1a, an intervening dielectric layer 105 and a metal pad 120 are formed over a semiconductor substrate 100. Here, a titanium layer 110 is formed under the metal pad 120, while a titanium nitride film 125 is formed on the metal pad 120.
Referring to FIG. 1b, a passivation layer 130 is formed on an entire surface including the metal pad 120.
Referring to FIG. 1c, a first photoresist pattern (not shown) is formed over the passivation layer 130.
Here, it is preferable that the first photoresist pattern (not shown) is formed while the center of the metal pad 120 is opened.
Then, the passivation layer 130 is etched, using the first photoresist pattern (not shown) as a mask to expose the titanium nitride film 125, which is formed on the metal pad 120. Then, the first photoresist pattern (not shown) is removed.
Referring to FIGS. 1d and 1e, a curable polymide isoindro quirazorindione (PIQ) layer 135 is formed on an entire surface including the etched passivation layer 130.
A second photoresist pattern 140 is formed over the PIQ layer 135.
At this time, it is preferable that the second photoresist pattern 140 is formed while the edge part of the etched passivation layer 130 is not opened.
Then, the PIQ layer 135 is etched, using the second photoresist pattern 140 as a mask.
At this time, it is preferable that the PIQ layer 135 remains in the side wall of the etched passivation layer 130.
Then, the second photoresist pattern 140 is removed.
Referring to FIG. 1f, a curing process is performed for the PIQ layer 135.
The PIQ layer 135 is condensed by the curing process. Due to this, the PIQ layer 135, which was formed on the side wall of the etched passivation layer 130, retrogrades into the upper portion of the passivation layer 130. Therefore, the region opened by the PIQ layer 135 is widened.
At this time, the RIO layer 135 is unable to cover the area over the outer ring of the metal pad 120 in the curing process, and a lifting phenomenon (see ‘A’) is generated.
Referring to FIG. 1g, the etching process is performed to remove the titanium nitride film 125 on the metal pad 120, so that the metal pad 120 is exposed.
FIGS. 2a to 2d are cross-sectional views showing another method of manufacturing a semiconductor device according to the related art.
Referring to FIGS. 2a and 2b, an intervening dielectric layer 205, a metal pad 220 and a passivation layer 230 are formed over a semiconductor substrate 200 with a method as illustrated in FIGS. 1a and 1b. A titanium layer 210 is formed under the metal pad 220, while a titanium nitride film 225 is formed on the metal pad 220
The passivation layer 230 is etched so that the passivation layer 230 of a constant thickness remains over the metal pad 220 such that the metal pad 220 is not exposed.
A PIQ layer 235 is formed on the entire surface including the etched passivation layer 230.
Referring to FIG. 2b, the PIQ layer 235 is etched in order that the PIQ layer 235 remains on aside wall of the etched passivation layer 230.
Referring to FIG. 2c, when the curing process is performed for the PIQ layer 235, the PIQ layer 235 is condensed so that the opened region is widened.
Here, while the PIQ layer 235 is condensed, the PIQ layer 235 formed on the side wall of the etched passivation layer 230 retrogrades into the direction in which the opened region is widened, so that it remains only over the passivation layer 230.
At this time, the lifting phenomenon A if the PIQ layer 235 is generated.
Referring to FIG. 2d, the etching process for removing the titanium nitride film 225 such that the passivation layer 230 remains over the metal pad 220 is performed.
At this time, a gap between the metal pad 220 excessively opened in the etching process generates an attack (see ‘B’) in the passivation layer 230.
In the manufacturing method of a semiconductor device according to the related art, there is a problem in that the metal pad is excessively opened due to the PIQ layer. Hence, the attack occurs in the subsequent PIQ layer etching process and the layer of the lower portion of the metal pad is damaged. Accordingly, the reliability of device is lowered.